This invention relates to droplet deposition apparatus and especially to ink jet printheads. In particular it relates to methods for attaching the nozzle plate to the printhead body.
It is known in the art of ink jet printing that problems with uneven printing, white lines, etc. can occur and that the cause of such printing defect resides frequently in the nozzles through which the ink droplets are propelled towards the ink receiving medium. The printing defects mentioned above can be caused by clogged nozzles, e.g., by drying of the ink in the nozzle or by impurities in the ink, by damaged nozzles, e.g., by the presence of hard pigments in the ink.
In SOHO (Small Office/Home Office) printers, when problems arise the printhead is discarded in its entirety and replaced. In larger ink jet printers larger printheads, even page wide printheads are used. A typical example of such a printhead has been disclosed in U.S. Pat. No. 5,855,713. This patent discloses a printhead with a body with a plurality of parallel channels therein, the channels terminating in a common channel termination plane and a nozzle plate mounted on the body at the channel termination plane. The body and the nozzle plate are firmly bound together so that when printing problems arise due to defects in the nozzles, the whole printhead has to be discarded, or else the rework in removing the nozzle plate and replacing it with a new one is a very cumbersome task. In printhead structures as described above the nozzle plate represents less than 20% of the cost price of the printhead. Thus, the user is almost forced to discard an expensive printhead of the printer because a fairly inexpensive part of it has a defect.
EP-A-0 703 082 discloses a printer wherein a nozzle plate is releasably attached to the printhead body by a clamp.
In JP-A-55 121081, a nozzle plate is releasably attached to the printhead body by means of a guide rail.
JP-A-63 064755 discloses nozzle plates that each have only a single nozzle; the nozzle plates are releasably attached to the printhead body by means of protrusions and grooves.
There is still need for an improved releasably attached nozzle plate.
It is an object of the invention to provide a droplet deposition apparatus comprising a nozzle plate that can easily be interchanged.
The above mentioned object is realized by a droplet deposition apparatus in accordance with the invention as claimed in claim 1. The dependent claims set out preferred embodiments of the invention.
In accordance with the invention, a nozzle plate is releasably attached to the printhead body by using an adhesive layer so that upon detaching the nozzle plate from the channel termination surface, there is an adhesive break between the adhesive layer and the channel termination surface and there is no cohesive break within the adhesive layer. An important advantage of the invention is that upon peeling by a shear force the nozzle plate is removed from the printhead body together with the adhesive layer. No or only a negligible residue of adhesive remains on the printhead body. Thus, if the nozzle plate has a defect, it is easy to remove the nozzle plate and the adhesive layer and to attach a new nozzle plate to the printhead body, thus reusing the printhead body.